What doesn’t kill you makes you stronger
Transformation Hardening
Anyone who took the Introduction to Materials Engineering course would probably understand what I’ll talk about.
In this course, the professor was explaining the behavior of materials is exposed to different conditions with their theoretical background. Even though I found his teaching style quite boring, learning the behavior of materials was fascinating!
That day he was talking about the mechanism of strengthening in metals. The grain-size reduction, solid-solution alloying, and strain hardening can be counted as the ways of strengthening single-phase metals. The main purpose of applying these methods is to modify and enhance the properties of the materials e.g. hardness. Hardness is defined as the resistance to surface deformation ( localized plastic deformation) and the ability to withstand scratching induced by mechanical effects.
The most famous and well-known metal is steel, therefore he firstly focused on the hardening mechanism in carbon steels. It is the carbon and alloying amount in the steel composition which named the type of steel. The type of steel and its hardening mechanism he mentioned was martensitic steel and transformation hardening respectively. The Martensite is formed as a result of rapid cooling from austenite which is an iron-carbon alloy that may exist above 723°C and below 1500°C depending on the carbon amount. In this transformation, the rapid quenching takes place at such a high rate that carbon atoms do not find time to diffuse out of the crystal structure. Therefore the change in microstructure results in the formation of a supersaturated, very hard form of crystalline steel structure.
When the professor was emphasizing the effects of severe conditions on materials during the transformation process, I was busy writing the following sentences in my notebook.
No need to do an experiment to understand the logic of the transformation hardening mechanism in metals,
Everyone and everything changes and become stronger when they are exposed to severe conditions
